Apparatus for making cast-in-place pipe



July 13, 1965 H. 5. LEE EI'AL 3,193,901

APPARATUS FOR MAKING CAST-IN-PLACE PIPE Filed NOV. 20, 1961 5Sheets-Sheet 1 INVENTORS: #525527 .5. LEE BY JAMES F. O'CQA IVEQ A T70245 Y5 July 13, 1965 H. 5. LEE ETAL 3,193,901

APPARATUS FOR MAKING CAST-IN-PLACE' PIPE Filed Nov. 20. 1961 5Sheets-Sheet 2 INVENTORS. 1 /525527 $.LEE JAMES F. O'CO/VJVEZ July 13,1965 Filed Nov. 20, 1961 A H i? H. 5. LEE EI'AL APPARATUS FOR MAKINGCAST-IN-PLACE PIPE 5 Sheets-Sheet 3 INVENTORS.

#525527 3. LEE JAMES F. O'CO/VA/EE ATTOE/YEYS July 13, 1965 H. 5. LEEETAL APPARATUS FOR MAKING CAST-IN-PLACE PIPE Filed Nov. 20. 1961 5Sheets-Sheet 4 INVENTORS: #525527 .5. LEE BY JAMES F OCO/VNEE ATTOR/VEYS July 13, 1965 v v H. 5. LEE arm. 3,193,901

APPARATUS FOR MAKING CAST-IN-PLACE PI-PE Filed Nov. 20, 1961 5Sheets-Sheet 5 INVENTORSI #525527 .9. LEE

BY JAMES E fl'COlVA/i? ATfOEA/EX) United States Patent APPARATUS FORMAKING -CAST-IN-PLACE FIFE Herbert S. Lee, Los Alamitos, and James F.Ofionner,

Long Beach, Qalii, assignors to American Pipe and Construction 630.,South Gate, Calit'., a corporation of Delaware Filed Nov. 20, 1961, Ser.No. 155,531 14 Claims. (6i. 25--32) This application is acontinuation-in-part of copending application, Serial Number 100,457,April 3, 1961, now abandoned.

This invention relates to apparatus for producing castin-place pipe. Theinvention more particularly involves the utilization of an inflatabletubular envelope that defines a core member for supporting cementitiousmaterial until it takes a permanent set.

Although the use of inflatable core members is not new, the methods andapparatus previously employed have not proven to be entirelysatisfactory, primarily since the cost of the inflatable core memberswas high compared with their life expectancy. Furthermore, pipe conduitsformed by the prior art systems tended to be of variable thickness,especially where the cast-in-place pipe diameter was of relatively largesize. In many instances this was the result of an inability to retainthe form member submersed at a uniform level within its cementitiousencasement, for, as might be expected, these form members tend to floator be buoyed up by the relatively heavy cementitious material.

Briefly, the present invention contemplates apparatus that can utilizean inflatable tubular envelope made of thin, pliable and inexpensivematerial. The envelope is initially sealed and anchored at one end by afirst bulkhead, through which the envelope is inflated with fluidpressure medium. A second bulkhead is provided at a spaced distance fromthe first bulkhead; and while this second bulkhead is advanced,increasing the inflated length of the envelope, the newly inflatedsectional lengths are progressively encased with cementitious material.By virtue of this progressive system of inflation and encasement, thecementitious material can be gradually deposited upon the envelope.Since the entire inflated surfaces of the envelope may be easilyconfined by the bulkheads and the cementitious material depositedthereon, there is little danger of rupturing a portion of a relativelythin envelope. Moreover, since the encasement process is continuous andprogressive, each newly inflated section of the envelope is capable ofbeing accurately positioned and supported while being encased with thecementitious material. Inasmuch as the fluidity of the cementitiousmaterial may be regulated so as to take a set soon after it is placedaround the envelope, only the most recently encased portion of theenvelope need be held against floatation. Thus, no special restrainingbraces are required for holding the inflatable envelope against theforces of buoyancy.

This invention also contemplates and provides new and different forms ofapparatus for encasing an inflatable tubular envelope with cementitiousmaterial. It will be readily apparent that new forms of apparatus havebeen discovered and devised for sealing oil the ends of the envelope bybulkhead means. Also, a movable bulkhead is provided that is adapted tobe advanced along the bottom surface of a trench during the process ofmaterial encasement. Novel forms of apparatus are also provided forextruding cementitious material around an inflatable tubular envelope asa movable bulkhead is simultaneously and continuously advanced.

Therefore, it is to be understood that one object of this invention isto provide new forms of apparatus for pro- F4 3,193,931 e Patented July13, 1965 ducing cast-in-place pipe, said apparatus utilizing aninflatable tubular envelope.

Another object is to provide apparatus for producing cast-in-place pipeincluding an inflatable envelope, having means defining a movablebulkhead for engaging said envelope and sealing off one end thereof, andwhereby said bulkhead means can be advanced along a path, therebyincreasing the inflated length of said envelope.

It is another object of this invention to provide apparatus of the kinddescribed in the above objects and further including means for extrudinga cementitious conduit around the inflatable envelope as said movablebulkhead is advanced.

Another object is to provide apparatus of the kind described whereinsaid inflatable envelope is packaged in a cartridge from which it iscontinuously withdrawn and extended as the apparatus is advanced.

Another object of the invention is to provide apparatus of the kinddescribed including a cartridge comprising a cylindrical sleeve having acoaxial center mandrel supported from a sealing bulkhead, andfurtherwherein an inflatable envelope is accordion folded upon said mandrelwithin said sleeve.

A further object of the invention is to provide apparatus of the kinddescribed wherein said inflatable envelope is formed of relatively thin,pliable material that may be folded.

Other objects of this invention will become more readily apparent inview of the. following description and the accompanying drawings.

In the drawings, forming a part of this invention and in which likeparts are identified by like reference numerals throughout the same,

FIG. 1 is a longitudinal vertical section of one form of apparatus forproducing cast-in-place pipe in accordance with the practice andteaching of this invention, certain parts being shown in elevation;

FIG. 2 is a partial top plan View of the apparatus shown in FIG. 1;

FIG. 3 is a section taken on lines 33 of FIG. 1;

FIG. 4 is an enlarged horizontal section of the stationary bulkheadshown in FIG. 1;

FIG. 5 is a section taken on lines 55 of FIG. 4;

FIG. 6 is an enlarged detail section taken on lines 66 of FIG. 5;

FIG. 7 is an enlarged section of a portion of the ap-' paratus shown inFIG. 1;

FIG. 8 is a perspective and detail view of a pinch roller assembly thatforms a part of a movable bulkhead;

FIG. 9 is a longitudinal vertical section of the apparatus shown in FIG.1 during the process of anchoring the movable bulkhead and disassemblingsaid bulkhead from the material encasement apparatus;

FIG. 10 is an elevational view of the form encasement apparatus of FIG.1 in a dismantled condition ready for cleaning;

FIG. 11 is a longitudinal vertical section of a second embodiment ofapparatus for producing cast-in-place pipe which utilizes an envelopecartridge, some parts being shown in elevation;

FIG. 12 is an enlarged detail view of the envelope cartridge assemblyshown in FIG. 11;

- FIG. 13 is an enlarged detail view of one portion of the cartridgeassembly, showing the way in which the inner end of the envelope issealed; and

FIG. 14 is a front end elevation of the cartridge assembly mounted uponits supporting skid. I

Referring to FIG. 1 in particular, there is shown a novel arrangement ofapparatus for producing cast-in-place pipe in a trench and generallycomprising an inflatable tubular envelope 10, a stationary bulkhead 11with air compressor means 12, a imovable bulkhead 14 forrextrudingcementitious material around the envelope 10, and power-drive means 15for advancing bulk head 13 and extrusion apparatus 14. a

c The inflatable tubularenvelope 10 may be'formed of I relatively thinpliable material such as plastic. While perhaps'many forms of plasticmaterials may be used, the product known as Mylar, manufactured by DuPont, has been satisfactorily employed. The, wall thickness of theenvelope may be extremely thin as compared with liners 13, extrusionapparatus 7 by the pinch rollers as the envelope passes through slottedopening 44' Inasmuch as the envelope Willbe forced against the wallmember 42 by the internal and confined fluid pressure, and since theenvelope is drawn frictionally across the wall member, it is desirablethat surface 43 be polished to reduce frictionaldrag and abrasivecontacts which would tend to rupture the envelope.

conventionally utilized in form pouring. For'exarnple,

an inflatable envelope having a'diameter of 24' may be formed frommaterial havin'g a wall thickness of only ;O1". This size of envelopeand material is given only a by way of example to illustrate that'theenvelope material may be relatively thin and expandable.

The useof lateral guide rollers 47 has also been used to advantage in anarrangementas shown in FIGS. 7 and 8. Rollers-47 serve to direct theenvelope into the slotted opening 44. a. Y

It is to be noted that this inventionfurther contemplates anovelassembly of extrusion apparatus 14 for continu- Envelope is fluidlysealed at a fixed or stationary end y by bulkhead 11, as shown inFIGS..46} A pre-cast sec- 7 tion of pipe 20, or other form member havingsubstan-- ftially the same internal circumference asthe exterior cir-fcumference ofthe envelope'10; is initially used to begin the processoflpipe manufacture.- Pipe section is re- 1 strained frombackward'movement by a bracing means comprising a pair of timbers 21 anda screw jack 22. One timber member is placed on either side ofthe'trench 23.within-which the pipe is to be cast, and the screw jack isused to spread the timbers apart, forcing them into the walls of thetrench. Each imber provides'a surface portion laterally inward of thetrench against which the cast-in-place pipe section is placed, saidtimbers restraining further rearward movement of the pipe section.

- Bulkhead 11 is comprised, of a wall member 24 having a peripheral rimZSdefining an exterior channel, and an inflatable tube 26 or otherexpan-sible means is disposed peripherally thereof; Tube 26 resemblesthe tire of a vehicle having a .valvejstem 27 protruding inwardlythrough rimZSL An elastic ring 28is used for securing 7 envelope 10peripherally of rim 25,bef0re bulkhead 11' is placed within a pre-castpipesection; and four quadrantly spaced fastening screws 29 are used foranchoring the bulkhead to the pre-cast pipe. I

ously and, progressively forminga cementitious. pipe around the inflatedportion of envelope 10. The extrusion apparatus comprises a" slip formtype of machine that is constructed'with :detachable front and rearwardskid 1 sections 59 and 51, verticallydivided as shown in FIG. 10 r andconnected by pins 52. The rearward section 51 defines a. tubular slip;form 53 having a hopper portion 54 communicating with a forward interiorportion-thereof.

' The front skid sectionSt) is attached to power-drive means 15 and alsosupports a tubularauger or'screw 55 upon a fixed, elongated sleevemember. 56. 'Sleeve member 56 is supportedat one end, havingits'rearward portion cantilevered coaxially'with respect to tubular slipform 53. Bearing surfaces 57and58- are provided exteriorly of sleevemember 56 and complementarybearing surfaces 59 and 6tareprovidedinteriorly'of the auger. Additionally, a thrust bearing andextension sleeve 61 is supported rearwardly of the, auger from the end'of sleeve member56. V

, The bearing surfaces 57,58, 59 and 60 are lubricated from a centralsupply source through a conduit. 62.

When the front and rearward sections 50 and 51 are assembledf'auger 55is coaxially disposed within tubular slip form 53. The auger transportscementitious material Wall member '24 contains a pair of pressure reliefvalves 1 30, each valve comprising a valve'plate 31 reciprocally 1mounted ona valve stem 32frorn a cross arm support 33 and biased towarda closed positionbya helical compres sion spring 34. A pair of lock nuts35 is'threaded upon the valve stem, andby rotatably adjusting theiraxial position thecompression force of the valve spring'srnay becontrolled. It will be apparent that the relief valves are employed tolimit thefluid pressure force applied withinv envelope 1t).

Compressor means 12, comprising a gasoline powered 7 engine 36 andblower 37, is fluidly connected to theinteriort of envelope 10 by aflexible conduit 38 through an opening in wall member 24. A secondconduit line 39 provides fluid communication between'the interior of theenvelope and a manometer 40, which indicates the instantaneous fluidsupporting pressure within said envelope. I

As indicated above, envelope'ltl is sealed off at its other end by amovable bulkhead 13; and while the bulkhead 13 is .advanced along trench23, the inflated length of the envelope is progressively increased. Thedeflated portion of envelope 10, i;e., the portion forward ofbulkhead13, maybe rolled upon a reel 41 and carried in ad vance of the bulkhead.r

Bulkhead 13 comprises awall' member 42 having. a

n from the hopper portion 54, feeding and'extruding the material aroundan interior slip form sleeve 63. Bulkhead 13,'sleeve 63 and extensionsleeve 61 are'brought into a unitary assembly by a plurality of'tie rods64 that are pivotally and detachably connected to ears 65 attachedinteriorly of sleeve 45; Each tierod extends through .the fixed sleev'emember 56 and is detachably secured to a clevis bracket 66 by means ofnuts 67. The clevis brackets are. rigidly mounted to the front sectionand,

accordingly, the extrusion apparatus 14 and bulkhead'13 move asaunitaryassembly.

a It will be seen that the reel 41 is" also mounted upon the frontsection 50, and the envelope material extends interiorly through sleeves63, Hand elongated, sleeve member 56.

' Auger is rotatably operated-by the power drive means 15 through atransmission comprisinga drive shaft 6S,'a sprocket 69, drive chain anda driven sprocket 71. Shaft 68-is journaledupon bearings 72 and 72amounted upon the front. section 54 and sprocket 69 is V keyed'to theshaft as shown in FIG; 7; The driven sprocket 71is attached peripherallyof the auger by means of a plurality o'fsetscrews 71a.

Drive means 15 com'prises a vehicular frame 73 that is connected to thefront section 50 by three pin conconcave, polished surface43 and acentrally slotted open-1 v ing 44. Wall member 42 is mountedwithin acylindrical slip form sleeve 45that; serves toprovide a continuation'nections 74, 75' and 76. Frame 73 is primarily sup ported upon a hightraction tire 77 which isused for propelling the 'casbin-placeapparatusalong the trench.

. The drive means 15 also includes 'a gasoline engine '73, a hydraulicpump 73 and two hydraulic motors 8t) and [81. Hydraulic motorSG is usedfor driving the high traction tire '77, andmotor 81 operates the augerdrive shaft 6fl through age'ar box 82 and a detachable shaft connection83. As shown and described, the drive means is formedasa power packagethat may be used with various size machines, grouped as to their powerrequirements. Thus, it will be' seen that the entire drive means can be'detached'from one extrusioh apparatus by re moval of pin connections 74,75 and 76, and detaching shaft connection 83. Then the same drive meanscan be connected to an extrusion apparatus of different size but havingidentical connections. This structural arrangement reduces the number ofpower units required to operate a full range of machines.

It is to be understood that while a preferred form of apparatuscontemplates a self-propelled machine having high traction tire,nevertheless the more fundamental principles of this invention can beused with machinery that is moved longitudinally of a trench by awinch-powered cable. In such instances an extrusion apparatus of thekind described is utilized, then separate power mechanism may beprovided for rotating the auger.

To start the process of casting a pipe in place, the piece of pre-castpipe 20, or a metal form, is placed within the trench 23. Timbers 21 andjack 22 are then installed for restraining the pipe against backwardmovement. The extruding machine, including movable bulkhead 13, isplaced adjacent to the pre-cast pipe section with the slip form sleeve45 actually disposed within said pipe section. Envelope is then pulledthrough the machine and pre-cast pipe 20 whereupon stationary bulkheadassembly 11 is secured thereto by elastic ring 28, said envelopeextending over the tube 26. The bulkhead assembly is slipped into therearmost end of the pre-cast pipe, and while supported in a verticalposition, tube 26 is inflated forming a fluid pressure seal. Afterinflation of tube 26, which centers the bulkhead 11 relative to pipesection 20, screws 29 are tightened to secure the bulkhead to the pipesection and thereby preventing the fluid pressure that is to be appliedwithin envelope 10 from blowing the bulkhead out of the pipe section.The apparatus is now conditioned to begin operation.

Blower means 12 is started, supplying air pressure into envelope 10 andcausing an inflation thereof between bulkheads 11 and 13. The amount ofair pressure used will necessarily depend upon the diameter of pipebeing cast as well as the wall thickness of the pipe. However, aninternal pressure of 6 oz./sq. in. has been effectively used in castinga pipe of 24" internal diameter. Inasmuch as the entire envelope iscontained by the more durable and rigid bulkhead surfaces and theinten'or confines of the pre-cast and cast-in-place pipe sections, thereis no tendency for the envelope to be enlarged beyond its normalinflated size, provided, of course, that the internal pressure does notbecome excessive. For this reason, and also to prevent rupturing of theenvelope, pressure relief valves 30 are utilized to insure that a nearconstant pressure level is maintained. The pressure level may be checkedby the manometer 40.

At this point of operation the movable bulkhead 13 and extrusionapparatus are ready to be advanced. From a control panel 84 mounted tothe rearward section 51 of the extrusion machine, operation of the augerscrew 55 is begun, taking freshly prepared concrete from the hopper 54and extruding it around slip form sleeve 63. As the extruded pipematerial emerges from the end of tubular slip form 53, which isinitially placed in approximate abutment with the pre-cast pipe section20, power is supplied to the high traction tire 77 and the movablebulkhead and extrusion apparatus are advanced. The speed of forwardmovement is made equal to the rate at which pipe material is extruded.Thus, envelope 10 is not subjected to any abrasion from the concrete;and the only abrasion encountered by the envelope is that which resultsfrom the contact with the polished surface 43 of bulkhead 13.

The machine may be continuously advanced until the length of a selectedrun is completed, as may be determined by the length of the inflatableenvelope, or the size of reel 41. For convenience of operation, it iscontemplated that the envelope material may be stored upon reels of 1000feet capacity.

After a given run has been completed, the extrusion machine 14 and drivemeans 15 can be removed from the trench for cleaning although the mostrecently extruded pipe sections have not taken a permanent set. Ofcourse, the movable bulkhead 13 must remain in the trench until theconcrete has set sufliciently for the arch portion of the pipe to standwithout the aid of air pressure. It is for this reason that the bulkhead13 is detacha'oly formed from the extrusion apparatus 14.

To remove the extrusion apparatus, the forward ends of tie rods 64 areinitially disconnected from their respectiveclevis brackets 66 and anextension rod is added to each rod forward of the drive means, as shownin FIG. 9. Each extension rod is then secured in the trench and inadvance of the drive means by bracing means 86, such as employed forrestraining the cast-inplace pipe section 20 from backward movement.Obviously, bracing means 86 is secured in a manner to prevent themovable bulkhead 13 from being moved forwardly by the air pressurewithin envelope 10 after the extrusion apparatus is removed. The lengthof the extension rods 85 need not be long but suflicient to allow theextrusion apparatus to be advanced about four feet. With bulkhead 13secured in place, the extrusion por tion of the machine is propelledforward about three feet, leaving the bulkhead in the extruded pipe andforming an access space between slip form sleeve 45 and sleeve 63.Braces are now applied between the slip form sleeve 45 of bulkhead 13and the trench, said braces being similar in type to that shown anddesignated as bracing means 86. Once bulkhead 13 is secured to thetrench, the tie rods 64 are disconnected from their respective ears 65,then tie rods 64 and extension rods 85 are removed from the trench. Inthis condition the extrusion apparatus 14 and drive means 15 may also beremoved from the trench. By removing the four pivot pins 52, the frontand rearward skid sections 50 and 51 may be separated for cleaning asshown in FIG. 10.

After a suflicient time has elapsed for the concrete pipe to take a set,the air compressor 12 may be turned 011 and the pipe exposed toatmosphere. Bulkheads 11 and 13 and envelope 10 are then removed fromthe pipe, and an end joint is provided.

A further development of the basic inventive concept is illustrated inthe embodiment of FIGS. 11-14. The extrusion apparatus 14a issubstantially identical to that previously described. The only majordifference is the elimination of the sleeve extension 63 and thesubstitution of an envelope cartridge assembly 113 in place of thebulkhead 13.

Cartridge assembly 113 comprises a cylindrical sleeve 114 having anenlarged, conical-shaped end and including a tubular center mandrel 115supported from a bulkhead 116. The inflatable envelope 10 is disposedwithin the cartridge assembly, being accordian folded, as shown in FIGS.11 and 12; and the inner end of envelope 10 is sealed by bulkhead 116 inthe manner shown in FIG. 13, where the envelope is initially passedaround the periphery of the bulkhead before said bulkhead is secured inabutment with a flange portion 117 on the end of sleeve 114. I

Angularly spaced ears 118, which may be formed integrally with theflange portion 117, extend radially inward beyond said flange portion,allowing the bulkhead to be secured thereto by studs 119 and nuts 119a.

Referring to FIG. 13, the flange portion 117 may be mounted withinsleeve 114 by a plurality of screw members 120 inserted radially throughthe sleeve. It will also be seen that a resilient gasket 121 is utilizedto more effectively seal the end of envelope 10 between flange portion117 and bulkhead 116.

Furthermore, in view of FIG. 12, it will be noted that sleeve 114 isprovided with a peripheral flange 122 at or near the point where the endof the sleeve enlarges.

Flange 1'22 serves to limit the forward movement of the sleeve relativeto the extrusion apparatus as the cartridge 7 7 V sleeve is placedwithin the slightly greater diameterthan the inner diameter of sleevemember 56. Cartridge assembly113 is loaded into sleeve member 56 fromthe rear and is securedtherein by the connection of a retainer bar 123,as best shown in F-IG.

14. Bar 123 may be fastenedto the same stud mem- "bers 119 which connectbulkhead 116 to flange portion 117, but by the supplementary use 'ofnuts 111k. 'The ends of bar 123 are sufficiently extended to overlap theforward end of sleeve 56,,thereby preventing a rearward,

removalof the cartridge until the. bar is itself removed.

auger 55, said flange being of Thus, flange 122 and the retainerbar 123confine cartridge assembly113 within sleeveSd.

As with the first described embodiment it is desirable that theextrusion apparatus should be remov'able'from the trench for cleaningalthough the most recently cast pipe has not hardened sufiiciently to beself-supporting. The embodiment of FIGS, 11-14 utilizes a novelsystemfor removing cartridge assembly 113 while the last-poured pipe sectionis hardening. Of course, it'is again necessary that the pressure withinenvelope 10'be maintained if the cartridge is removed before thelast-poured ma? terial has solidified, and'the system shown isinherently capable of performingthis function. In the initial setting upof the apparatus, a cable 124 is hooked to the stationary. bulkhead 11by means of a hook attachment 125 V any air which may escape from smallleaks without adversely affecting the pressure to be maintained.

In operation, the extrusion apparatus 14a with envelop cartridgeassembly 113 is advanced along the trench; and

as the machine is advanced the infolds of the envelope are extendedand'inflated. Cable 124 is simultaneously lengthened, being drawn offroll 126 and through the bulkhead 116. Now, as the machine nears the endof its intended run, for example, when the envelope ltl is nearly 'fullyextended, a cable clamp 127 is applied. to;

cable 124 in frontof bulkhead 116. 7 Cable clamp 127 will be drawn intoabutting engagement with the bulkhead, thereby preventing a furtherextension of thecable.

126 may be removed from'itssupport onthe extrusion At this point, andbefore any tensionis applied to the. cable, the retainer bar 123 isremoved; and either roll apparatus or the cable may be disconnected fromthe roll itself. The extrusion apparatus 14a may then be ad-i vanced andcable 124 will hold the cartridge assembly. 113 in.place.

' While the last-laid pipe section is hardening, the extrusion apparatus14a may be dismantled and cleaned in i the same manner shown in FIG. 10.It will be under stood that the cartridge assembly 113 will remain inplace in the trench until envelope ltlcan be de-pressurized' after whichtime the cartridge is removed and reloaded with another envelope. j e

* It is to be understood that the forms of the'invention herewith shownand described are to be taken as preferred examples thereof. Althoughvarious changes may be made without departing fro'm'the spirit of theinvention or the scope er the attached claims, each of such changes iscontemplated and is to invention. p

Having thus described ut invention, what we desire to secure by LettersPatent is: v

1. Apparatus for producing castsin-placejpipe comclaim and be regardedas part of this tionary end extending rearwardly from said skid and asealed front end disposed within saidrcartridge, means for inflatingsaid' tubular envelope intermediate said sealed ends withsufficientpressure to sustain a layer of cementitious' material, andmeans supported from said skid'for progressively encasing saidenvelopewith inaterial as said skid and cartridge are advanced;

2. The apparatus of claim l'wherein said encasing meanscomprisesextrusioh apparatus adapted for being operated to produceextruded pipe at a linear rate equal to the forward movement of saidskid, said extruded pipe having approximately the same internal shapeandsize as the exterior shapeand size of said tubular envelope. 7 3. Theapparatus of claim 1 wherein said cartridge comprises a cylindricalsleeve having a coaxial center mandrel'supported upon a substantiallyhorizontal axis, and wherein uninfiated portions of said envelope areaccordion folded upon said mandrel within said sleeve.

4. The apparatus of claim 1 and further including means of limitedextension.interconnecting the stationary and front ends of saidenvelope, said means allowing the inflated length of said envelope to beincreased up to the point of limited extension.

5; The apparatus of claim 1 wherein said inflatable envelope iscompactly arranged in concentric accordion folds and disposed Withinsaid cartridge,

6. Apparatus for producing cast-in-place pipe comprising: a tubular skidhaving a hopper communicating with a forward interior portion. thereof,a tubular screw coaxially disposed within said tubular skid and adaptedfor feeding and extruding material from said hopper rearwardly throughsaid 'skid,means for rotating said screw,

' means defining an envelope cartridge supported from said teriaL'andmeans for advancing said skid and forward bulkhead, at a linear ratesubstantially equal to the rate at which material is being extruded bysaid screw.

H '7. Apparatus for producingcast-in-place .pipe comprising: a tubularskid having a hopper communicating with a forward in-terior'portionthereof, a tubular screw coaxially disposed within said tubular skidadapted for feeding and extruding material fromsa-id hopper rear- Wardlythrough saidskid, means for rotating said screw, an envelope cartridgesupported from said skid centrally of said screw, a folded butinflatable tubular envelope disposed within; said cartridge, saidenvelope having .a sealed stationary end extending rearwardly from saidskid and a sealed front end disposed within said cartridge, means forinflating said tubular envelope intermediate said sealed ends withsufficient pressure to sustain a layer ofcementitious material, andmeans foradvanc'ing said skidand envelope cartridge at a'linear rateequal to the rate at which material is extruded by said screw.

8..The apparatus of claim, 7 and further. including means of limitedextension interconnecting the sealed stationary end and the sealedfrontend of said envelope, said means allowing the inflated length of saidenvelope to be'increased up to-thei point of limitedextension.

- '9. The apparatus of claim 8 wherein said :means of limited extensioncomprises 'a cable that extends through anopening in one sealed end ofsaid envelope; and further includes a cable clamp larger than saidopening, said cable clamp being attachable to'said cable for engagingsaid one sealed end and preventing further advancement prising:askidadapted to be moved longitudinally along the ground, anenvelopecartridge supported from said. skid, a folded but inflatable.tubular envelope disposed within said cartridge, said envelope having asealed staof 's'aidenvelope cartridge.

10. The apparatus of claim.9 and'further including a "cable reeladaptedfor feeding out said cable upon advancement of said envelope cartridgeuntil said cable clamp is attached to said cable and engages said onesealed end.

11. Apparatus for producing cast-in-place pipe comprising: a tubularskid having a hopper communicating with a forward interior portionthereof, a tubular screw coaxi-ally disposed within said tubular skidand adapted for feeding and extruding material from said hopperrearwardly through said skid, means for rotating said screw, an envelopecartridge coaxially disposed within said tubular screw, said cartridgeincluding a cylindrical sleeve, a conical end, and a coaxially disposedmandrel, said conical end extending from said cylindrical sleeve to saidtubular screw, a folded but inflatable tubular envelope disposed withinsaid cartridge, said envelope having a sealed stationary end eXtendingrearwardly from said skid and terminating at a first bulkhead and asealed front end disposed within said cartridge at a second bulkhead,means for inflating said tubular envelope intermediate said bulkheadswith sufiicient pressure to sustain a layer of cementitious material,and means for advancing said skid and envelope cartridge at a linearrate equal to the rate at which material is extruded by said screw.

12. The apparatus of claim 11 and further including means of limitedextension interconnecting said bulkhead-s, said means allowing theinflated length of said envelope to be increased up to the point of saidlimited extension.

13. The apparatus of claim 12 wherein said means of limited extensioncomprises a cable that extends through an opening in said secondbulkhead of said envelope, and

further includes a cable clamp larger than said opening, said cableclamp being attachable to said cable for engaging said second bulkheadand preventing further advancement of said envelope cartridge.

14. The apparatus of claim 13 and further including a cable reel adaptedfor feeding out said cable upon advancement of said envelope cartridgeuntil said cable clamp is attached to said cable and engages said secondbulkhead.

References Cited by the Examiner UNITED STATES PATENTS 291,849 1/84Howson 32 830,204 9/06 Boyle 25-32 857,584 6/07 Boyle 25128 857,586 6/07Boyle 2532 857,588 6/07 Boyle 25-32 1,348,332 8/20 Stremel 264311,636,243 7/27 Rasmussen 25--l27 2,125,025 7/38 Huckfeld-t et al 18562,206,410 7/40 Lolly 25128 2,878,544 3/59 Dilday 2532 2,950,702 8/Ferguson et al. 25127 FOREIGN PATENTS 570,970 7/45 Great Britain.

360,146 11/31 Great Britain.

13,054 1/ 12 Great Britain.

ROBERT F. WHITE, Primary Examiner.

ALEXANDER H. BRODMERKEL, Examiner.

1. APPARATUS FOR PRODUCING CAST-IN-PLACE PIPE COMPRISING: A SKID ADAPTEDTO BE MOVED LONGITUDINAL ALONG THE GROUND, AN ENVELOPE CARTRIDGESUPPORTED FROM SAID SKID, A FOLDED BUT INFLATABLE TUBULAR ENVELOPEDISPOSED WITHIN SAID CARTRIDGE, SAID ENVELOPE HAVING A SEALED STATIONARYEND EXTENDING REARWARDLY FROM SAID SKID AND A SEALED FRONT END DISPOSEDWITHIN SAID CARTRIDGE, MEANS FOR INFLATING SAID TUBULAR ENVELOPEINTERMEDIATE SAID SEALED ENDS WITH SUFFICIENT PRESSURE TO SUSTAIN ALAYER OF CEMENTITIOUS MATERIAL, AND MEANS SUPPORTED FROM SAID SKID FORPROGRESSIVELY ENCASING SAID ENVELOPE WITH MATERIAL AS SAID SKID ANDCARTRIDGE ARE ADVANCED.